This section introduces aspects that may help facilitate a better understanding of the disclosure. Accordingly, these statements are to be read in this light and are not to be understood as admissions about what is or is not prior art.
Recently, energy harvesting through sustainable approaches has become of interest not only to address the global energy crises but also to provide power for micro-scale electronics and sensors in emerging applications such as wearable and implantable devices. An assortment of technologies has been developed to transform environmental energy into electrical power via a variety of mechanisms, including electromagnetic, electrostatic, piezoelectric, and recently, triboelectric processes. Triboelectric nanogenerators (TENG) are highly capable of efficiently harvesting ubiquitous mechanical energy, hinged on principles of contact triboelectrification and electrostatic induction, and have received considerable attention in recent years. See Wang, Zhonglin, Triboelectric nanogenerators as new energy technology and self-powered sensors—Principles, problems and perspectives. Faraday Discuss, 2014, 176, 447-458. Ongoing efforts are primarily focused on augmenting power generation by increasing triboelectrification surface area, engineering the physical/chemical properties of contacting surfaces and implementing practical applications. Most of the demonstrated TENGs were built based on synthetic polymers for the ease and cost of manufacturability. However, TENGs utilizing naturally abundant biological materials has received considerably less attention. Obstacles concerning practical, eco-friendly utilization of TENGs such as the intricate fabrication and expensive machinery continue to prevail.
Chitosan is a natural and biodegradable biopolymer generally derived from chitin which is one of the main components of marine crustacean shells. Every year, 6 million to 8 million tons of sea creature shells are produced globally as waste products of food processing Most of them are dumped in landfill or the sea. A sustainable way to utilize this cheap and abundant resource will greatly benefit both economies and the environments. Recently, chitin and chitosan begin to be used for a few areas, such as water treatment, drug delivery, cosmetics, and tissue engineering. However, due to the seasonal and variable supplies of shells resulting in microscopically heterogeneous physical and chemical properties, the large-scale application of chitin or chitosan is not fully developed yet.
Chitosan and its reaction product may offer a valuable opportunity as potential constituents in biomedical devices. The vast disparity in structure and surface properties make it finely tunable for controlled degradation which is desirable in implanted applications.
There remains a need to develop new chitosan biopolymers and explore the new utilities of such chitosan biopolymers.